The goal of the Biometry Core is to provide data management and computing support for all projects, and collaborate with project investigators in the development and application of statistical methods for design and analysis. The specific aims of the Biometry Core are: 1. To provide statistical collaboration in the design, execution and analysis of all projects. 2. To develop procedures for data collection and maintain computer databases for information storage and retrieval. 3. To provide interim reports on individual study progress. 4. To interpret the statistical and prevention literature relevant to all projects, and to develop new study design and analysis procedures for skin cancer research. The biostatistical and data management support offered by the Biometry Core is essential to the successful completion of the proposed studies. A detailed assessment of sample size requirements and constraints has been considered during the design of all studies to assure adequate statistical power to detect effects of biological and clinical importance. Data collection and quality control procedures have been designed to reduce sources of extraneous variation, which could otherwise mandate large sample sizes. Statistical expertise has been central to the proper analysis and interpretation of past experimental results, and will continue to have a central role in the studies proposed in this competitive renewal.